Process of producing magnesium.



Uurra suArEs ATENT Faro.

FRANZ VON KU'GELGEN AND GEORGE O. SEWARD, OF HOLCOM BS ROCK, VIRGINIA,

ASSIGNORS TO VIRGINIA'LABORATORY COMPANY, OF NEW YORK, N. Y., A. CORPO- RATION OF NEW YORK. F

rrcocnss or rnonucmc MAGNESIUM.

Specification of Letters Patent.

Patented Feb. 2a, 1908.

Application filed June 9. 1905. Serial-N0. 264.506.

This'invention relates to the production of magnesium and magnesium alloys by electrolysis.

The present commercial process for the production of metallic magnesium consists in the electrolysis of the double chlorid of magnesium and sodium (or potassium). It is i very difficult to obtain the electrolyte free from water. The best results are obtained by mixing chlorid of magnesium with chlorid of sodium or of potassium, and carefully drying this mixture-and melting it. After certain other treatments the molten salt is poured into iron crucibles and subjected to an electrolyzing current while applying'heat externally. To get good results, the temperature has to be kept low and watched very carefully. If it rises too high, the magnesium is redissolved in the electrolyte; and furthermore the magnesium rises to the top where it is partly burned by exposure to the air, and partly recombines with the chlorin. Even where the proper temperature is maintained, the difference in specific gravity is' so, slight that it is necessary to use diaphragms of porcelain, which are expensive and fragile. Another disadvantage is that after a certain amount of magnesium has been removed by electrolysis, the electrolyte contains too much sodium or potassium for continuing the process; it then becomes necessary to remove it and replace it by fresh electrolyte. Thus the preparation of the electrolyte re- (Spires a long and tedious treatment; and t e electrolytic process is not continuous,'re quires great care, and necessitates the use of expensive diaphragms. Under these conditions' it has been heretofore impossible to produce magnesium at a low price, although the raw material is cheap. The present invention'eliminates the disadvantages of the prior process, and renders it possib e to produce magnesium by a continuous process, and at a considerably lower cost than heretofore. g 1

Our invention is based upon the discoverythat magnesium oxid or analogous magnesium compound is soluble in certain flworids of higher decomposition voltage, so t'l iat when such fused bath is subjected to electrolysis the magnesium compound alzone is decomposed and magnesium is separated-at the cathode. Wehave found that-a continuous electrolytic production of magnesium is ossible by the use as an-eleetrolyte of a used mixture of magnesium oxidr and magnesium fluorid, rendered fusibleby the. addition of a fluorid or'fiuoridszof, metals more electro-positive than-magnesium.- Magnesium oxid has a lowendecompnsition voltagethan magnesium fluoridr and the other fluorid or' fluoride, and is: therefore'decomposed in preference" to the othercompounds, solong as the voltage iskept'within certain limits, and aproper concentrationv is maintained. -By feedlng magnesium oxid to the electrolyte. inpro ortionas itvis decomposed,

the process may e carried on continuously. In case the voltage is hi her than the normal, some magnesium fluori d is also decomposed, but this is easily replaced by the addition of magnesium'fiuorid during the electrolysis.

In practicin the process, the solvent bath may be consi erably varied. -The mixture is chosen with a view of getting as low a melting point as o ssible consistent with the property of disso vlng magnesium oxid. A

mixture of mag'nesiumfluorid w th one or more alkaline fluorids is suitable. Or ma nesiumfiuorid, one or more alkaline fluori and one or more alkahne earth fiuorlds may be used. A nnxture of two parts magnesium .fluorid, one part lithium fluorid and one part calcium fluorid gives good results;

Instead of magnesium oxid, we may use magnesium oxy-chlorid or other oxy-comound which will dissolve in the solvent baths already described. In case the oxychlorid is used, both oxygen and chlorm are separated at the anode. Hereinafter, whenever We designate magnesium oxid, it is understood that we include the ox -chlorid of ma nesium or any other suitab e oxycompoun An example of an application of our invention is as follows :-A mixture of O aF 'ium fluorid. The combine 'ected to electrolysis in. any suitable and and MgF in any suitable proportions is melted in a suitable vessel, and when sufii- .ciently molten, MgO is dissolved therein. Or

the solvent bath may be made of any of the fluorids referred to, and may or may not include a lithium compound, referably lithd bath is subown manner. Carbon anodes may be used and an iron cathode, but other mate- 7 rials may be used for the anode and cathode.

Asthe magnesium oxid is decomposed it is I 'to be re laced by feedinggn fresh magnesium oxid. I t is desirable to eep the bath nearly saturated with the magnesium oxid, and the latter should therefore be fed in at frequent intervals, and as much ornearly as much as will freely dissolve.

[If it is desired to produce an alloy of magnesium, We. may use the alloying metal as the cathode, with which the separatedrnagnesium alloys, using for example aluminium,

as set forth in our applicatlon Serial No.

257,618, filed April 27, 1905.

'We claim as our invention 1., The process of producing magnesium which consists in dissolvin magnesium oxid in a fused'bath of mixed uorids whose decomposition voltage is higher than that of magnesium oxid, subjectlng the same to electrolysis, and feeding magnesium oxi'd to 'replace that whichis decomposed.

2. The process of croducing magnesium which consists in disso ving magnesium oxid in a fused bath of magnesium fluorid and another fluorid whose decomposition voltage is higher than that of magnesium oirid, subjecting the same to electrolysis, and feeding magnesium oxid to replace that which is de composed.

3. The process of producing magnesium which consists in dissolving magnesium oxid in a fused bath of magnesium fluorid and one or more alkaline fiuorids', subjecting the same to electrolysis, and feeding magnesium oxid to replace that which is decomposed.

4. The process of producing magnesium by dissolving magnesium oxid in a fused bath of magnesium fluorid and one or more fluorids of metals more electro-positive than magnesium, and subjecting the same to elecsigned our names in the presence of two subscribing witnesses.

FRANZ VON KUGELGEN. GEORGE O. SEWARD.

' Witnesses:'

Gno. 'T. .LANc 'sTER, C. OFFERHAUS. 

